Characters set koi8-r and windows-1251

Hello !
Have anybody expirience handling characters sets koi8-r and windows-1251
?
I'm plan to create corporative mail web archive, and we really need to
convert headers and body from windows-1251 to koi8-r.
Yes, i know about CHARSETCONVERTERS resource, but it seems
to lack support for Russian language. By search in mail archive i found
same problems with Hungarian, but no solution.
I will try to write appropriate converting module by myself, but if
somebody already have this work done...
Alexander Derevyanko, System Administrator.